This Knowledgebase article provides recommendations and considerations about Neverfail Channel configuration when deploying Neverfail in a LAN or WAN environment.
Neverfail recommends the following when considering configuration of the Neverfail Channel:
Both the Primary and Secondary servers must have two or more network interface connections (NICs).
- One NIC will be required for the corporate (public) network.
- One or two separate NICs will be required for the Neverfail Channel. The Channel is a private connection between the servers, which is used for control and data transfer between the Primary and Secondary server. The configuration will depend upon the network implementation:
In a LAN configuration (where both servers have the same corporate (public) IP address), Neverfail recommends three NICs: one for the corporate (public) connection, and either:
two for the Neverfail Channel
- one for the Neverfail Channel and one to act as a management NIC
In case 1 above, note that in order to provide added resilience, the communications for the second channel should be completely independent from the first channel, i.e. they should not share any switches, routers or the same network route. The second channel does not provide for additional throughput.
In case 2 above, the Split-Brain Avoidance function should be enabled using the management IP addresses to ensure high availability.
In implementations where there is only one channel connection, or where two channels share infrastructure, a failure of the connection could result in a split-brain condition, which should be considered in the design of the implementation. In applications where high availability is not required, the pair should be configured for manual failover.
A WAN implementation describes the configuration where the corporate (public) IP addresses of both servers are different. In this case, you must have an Active Directory integrated DNS for Neverfail to update the IP address when the pair undergoes a switchover or failover.
Neverfail recommends two NICs:
- One NIC for the corporate (public) connection
- One NIC for the Neverfail Channel
It is also recommended that the Split-Brain Avoidance function be enabled, however in order to guarantee high availability there must not be a single point-of-failure between the server pair. For more information about how to configure Split-Brain Avoidance, please see:
Knowledgebase article #838 - How to Configure Network Monitoring and How to View Network Status for Neverfail Heartbeat v5.x
Knowledgebase article #2040 - How to Configure Network Monitoring and How to View Network Status for Neverfail Heartbeat v6.x
There is no benefit in a second Neverfail Channel in most WAN implementations. For true high-availability in a WAN, you will need a second independent WAN connection, which will allow the public NIC on the remote server to be contacted even when the main WAN connection is unavailable.